During the course of a day, a foot, trapped within the confines of a conventional article of footwear, has a tendency to become hot and sweaty. This can cause a number of issues including poor foot odour and fungal infections such as athlete's foot. In these situations, an article of footwear that is better ventilated can cool and help to remove moisture, thus improving the unhealthy conditions within the footwear.
The prior art contains a number of examples of ventilated footwear; both those that employ a selectively permeable membrane and those that are provided with a pump. In both cases, the conventional designs have their drawbacks.
Footwear with selectively permeable membranes are limited in their effectiveness because the same qualities that make the membrane impervious to water also limit the amount of air that can pass through them. These designs usually include a membrane that is mounted above a perforated outsole and are susceptible to blockage as mud and dirt build up on the bottom surface of the sole.
Conventional pump-ventilated footwear is characterized by a pump mounted in a cavity within the sole and comprising a resilient chamber in communication with inlet and outlet check valves. In particular, the inlet valve controls the supply of air from outside the footwear while the outlet valve controls flow into one or more ventilation passages for distributing the air through the footwear. Due to the wearer's weight, during walking the sole of the footwear tends to be downwardly pressed and this pressure acts to compress the chamber in the sole, forcing air through the outlet valve into the shoe cavity. When the footwear is raised from the ground, the chamber is restored by the inherent resilience of the pump such that is will return to its default undeformed state, drawing in another charge of air.
U.S. Pat. No. 1,660,698 describes a prior art shoe where the pump chamber is formed as a resilient bellows or bladder received in a recess in a conventional relatively rigid heel, adjacent a flexible inner sole. U.S. Pat. No. 4,601,441 provides another example of prior art but where the pump chamber is formed as a cavity directly in a resilient sole.
In conventional pump-ventilated footwear, such as the aforementioned examples, the wearer's weight is supported by an air chamber in the sole; and the amount of ventilation is largely dependent on the amount of deformation of the sole during walking. For increased ventilation, the air chamber must be made larger or be made to deflect more, and thus the vertical movement of the foot within the shoe body sole must be increased or the lateral (horizontal) size of the pump increased, or both. All of these factors disadvantageously decrease the stability of the shoe, particularly in the lateral direction. To avoid this lack of stability with this type of footwear article, the amount of deflection and the size of the chamber, and consequently the displacement of the pump, are often relatively small in designs that are commercially available. FIGS. 1a and 1b illustrate the operation of a pump mechanism in such a conventional footwear article in that a pump member of the pump mechanism operates in response to the deformation of the shoe sole. Accordingly, it has been difficult to design inexpensive and reliable footwear of this type that provides good and practical ventilation for wearers with satisfactory stability.
Another drawback associated with conventional pump-ventilated footwear articles is that they typically provide ventilation only when the wearer's body weight is forced against the heel; and not during any other part of the walking motion.
A further disadvantage of conventional ventilated footwear is that they may not be suitable for wearing in cold climates. This is because external cold air would be undesirably drawn to the shoe cavity by the pump or through the selectively permeable membrane.
The present invention seeks to address the aforementioned problems in ventilated footwear. Furthermore, the invention seeks to take advantage of the air circulation in the footwear by introducing improvements which include means to circulate warm air, a deodorant, antiperspirant and/or fragrance.